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Hairy Chinch Bug

Ravageurs et maladies

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English

Hairy chinch bug.

Photo: Jardin botanique de Montréal (Michèle Roy - MAPAQ)

Onglets

Description

Summary

Hairy chinch bugs damage lawns by piercing the stems and leaves of grasses and sucking the sap. The toxic enzymes they inject when feeding cause grass stems to wilt and die, exacerbating the damage caused by their mouth parts. Lawns planted on sandy soil, in full sun and subject to drought are the most vulnerable to chinch bug infestations. Other contributing factors include setting lawnmower blades too low, heavy thatch and excessive feeding with nitrogen fertilizers.

Signs and symptoms

The first signs of an infestation usually appear from mid-July to mid-August. They take the form of small yellow patches in a lawn that eventually turn straw brown. Over time, the patches spread, forming large areas of dead turf when weather conditions encourage the insects to proliferate.

The first symptoms often appear near hedges, trees and ornamental borders.

Damage is usually limited in area, because chinch bugs feed as a group.

Infested areas are usually invaded quickly by weeds.

Suggestion : Given that similar damage is caused by drought, it is best to conduct one of the tests described below to determine whether chinch bugs are responsible for brown patches.

Latin name (genus)

Blissus leucopterus hirtus

Host plants

The most susceptible grass species are fine fescue, perennial ryegrass and, to a lesser extent, Kentucky bluegrass. Varieties of fine fescue and perennial ryegrass enhanced with endophytes (fungi) are more resistant, however.

Development cycle

Description and life cycle

Hairy chinch bugs belong to the order Hemiptera and the suborder Heteroptera. Their life cycle includes three stages: egg, larva and adult.

Eggs: Elongated and oval, 0.84 mm long and 0.25 mm wide. They are white when first laid, and turn yellow and then bright orange with a white band as they age.

Larvae: Resemble adults, but smaller (0.9 to 3 mm) and with a white band across the middle of their backs. The larvae pass through five growth stages before becoming adults. Wing pads appear during the third stage. The larvae also change colour as they develop. The first two stages are red, the third is orange, the fourth orange brown and the final stage black.

Adults: Adults are black with shiny, transparent wings. These are tiny insects (1 to 2 mm wide and 3 to 5 mm long) with antennae composed of 4 segments. The segments nearest the head and legs are purple. The white wings, held flat against the insect's body, form a distinctive pattern with a black dot on the outside margin of both forewings. Above the two dots is a black Y-shaped line with the open end pointing toward the head. Some individuals have shortened (brachypterous) wings, preventing them from flying.

Adult hairy chinch bugs overwinter in sheltered locations like plant litter, beneath bark, under hedges, in bushes, along roadways and in various building structures. The adults emerge from hibernation when air temperatures reach 7°C.

In spring, each female lays over 200 eggs, at a rate of about 20 a day. The egg-laying period lasts at least 3 weeks, reaching its peak in early June. The females lay their eggs on turf grass, in thatch and on the soil in warm, dry spots.

The larvae emerge 3 to 4 weeks later. Most 2nd and 3rd instar larvae are present in July. It is at this stage in their development that treatment is most effective. It takes 3 to 4 weeks for the larvae to reach adulthood.

Identification

To determine whether chinch bugs are responsible for damage, it is best to conduct one of these tests:

Flotation test: Remove both ends from a tin can (about 20 to 25 cm in diameter) and plunge one end of it 3 to 5 cm into the soil on the edge of a damaged area. Fill the can with water and scratch the lawn surface inside the can. If the lawn is infested with chinch bugs, they will float to the surface within a few minutes. Repeat the test in a few affected areas. Count the number of insects (see When to act).

Flannel sheet test: Drench the patch of brown grass and an area 60 cm wide around it with soapy water (mix 25 ml of dish soap with 4 litres of water) and then cover this area of the lawn with a white flannel sheet. The chinch bugs will cling to the sheet to escape the soap. Count the number of insects on the sheet after 15 to 20 minutes (see When to act).

Prevention

A lawn mown to 7.5 cm will be more vigorous and thus better able to withstand attacks by hairy chinch bugs. Only the first mowing in spring and the last mowing in fall should be shorter. Mowing your lawn to 5 cm early in the season stimulates grass growth and, late in the season, prevents diseases from developing.

Because chinch bugs flourish during hot, dry weather, watering your lawn may hinder the development of the young larvae by encouraging the emergence of parasitic fungi like Beauvaria bassiana. Water your lawn as necessary during dry spells to reduce insect populations, paying attention to municipal watering restrictions.

Chinch bugs overwinter most successfully in thatch layers over 1.0 cm thick. Encourage thatch to decompose gradually by using such lawn care techniques as aeration and topdressing.

Chinch bugs prefer young grass shoots. Because the use of high-nitrogen fertilizers encourages the growth of new shoots, it is best to avoid heavy feeding with such fertilizers. Use slow-release natural fertilizers.

Use varieties enhanced with endophytes (Acremonium coenophialum and A. lolii) when reseeding your lawn. Endophytes are fungi that grow in association with some turf grass species, including fine fescue, tall fescue and perennial ryegrass, and release toxins (alkaloids) that repel or kill chinch bugs.

Sow seeds of broadleaf plants like dwarf white clover. Clover is not affected by drought, has the ability to fix airborne nitrogen and is not part of the chinch bug diet.

What to do

When to act: Treatment is appropriate if there are more than 20 chinch bugs per container with the flotation test or more than 150 insects per m2 with the flannel sheet test.

Physical control

Before applying these control methods, it is best to mow your lawn to 5 cm.

Go over an affected patch and the area 60 cm around it with a Shop-Vac-style vacuum to pick up adults, larvae and eggs. Inspect your lawn regularly from late June to late July to detect the presence of chinch bugs. If your lawn was infested the previous year, begin vacuuming it in late May in order to catch the females before they start laying eggs.

Small-scale infestations may be controlled with the flannel sheet method. Drench the patch of brown grass and an area 60 cm wide around it with soapy water (mix 25 ml of dish soap with 4 litres of water) and then cover this area of the lawn with a white flannel sheet. Wait about 15 minutes and then vacuum off any insects clinging to the sheet or drown them in a tub of soapy water.

Biological control

Hairy chinch bugs are indigenous to North America. A wide variety of predators, parasites and diseases help to significantly reduce populations of these insects. Avoid using pesticides in order to protect these useful organisms.

Although many studies have attempted to come up with an effective solution based on the use of Beauveria bassiana fungus, none have yet proved successful.

Chemical control

The Montréal Botanical Garden does not recommend the use of pesticides to control hairy chinch bugs.